| With the rapid development of China’s economy,the investment in infrastructure construction in all walks of life has also expanded,and a large number of sand and stone excavation and utilization activities have been carried out,resulting in an increasing shortage of sand and stone and other materials.At the same time,in Sichuan,Chongqing and many other regions of China,due to abundant rainfall,there are a large number of over wet soils with poor engineering properties.These soils are often treated as spoil in engineering,resulting in the occupation of cultivated land and farmland.If these spoils can be treated and effectively utilized to make them into soil with good engineering properties,it will save a lot of sand,stone and other materials,so as to reduce the damage to natural resources and be conducive to the sustainable development of ecological society.According to the above,this paper uses the water reducing and compaction increasing powder and liquid agent independently developed by Southwest University of science and technology for soil improvement treatment,and then uses them for subgrade filling.The research results are as follows:（1）The indoor geotechnical test results show that the soil sample taken on site is silty clay,which has high moisture content,poor water stability and poor grading,so it can not be directly used as subgrade engineering filler.（2）Through the study on the influence of the amount of curing agent on the compaction performance of silty clay,it is obtained that the optimal amount of soil stabilizer is 2%;The optimal dosage of soil water reducing and compaction increasing powder is as follows: when the moisture content of natural soil is 18%,the powder dosage of 6% is the optimal dosage,when the moisture content of natural soil is 22%,the powder dosage of 12% is the optimal dosage,and when the moisture content of natural soil is 25%,the powder dosage of 15% is the optimal dosage.At this time,the dry density of the solidified soil is more than 7.39%higher than that of the original soil,the unconfined compressive strength is 45.93% higher,and the compression coefficient of the solidified soil is 62.5% lower than that of the original soil under the same pressure.Through the comparative analysis of natural soil and treated soil,it is obtained that the factors affecting the compaction mechanism and basic mechanical properties of soil are: water content,poor particle gradation,dry density,compressibility,degree of compaction and so on.（3）Through the indoor model test,the parameters of the filling and compaction construction technology,bearing characteristics,slope failure shape and settlement of each group of solidified soil are as follows: the filling height of the solidified soil model is 50 cm,which is divided into three layers.The filling thickness of the first layer is 20 cm,the second layer is15 cm,and the third layer or the uppermost layer is 15cm;The bearing capacity of each group of solidified soil is more than 125%,200% and 400% higher than that of natural soil or original soil,and the horizontal displacement is reduced by 92%,93.3% and 96%.The test results show that the soil mixed with curing agent is obviously conducive to improve its mechanical properties,reduce the water content in the soil and improve the degree of compaction.In addition,this paper also studies the impact of on-site rainfall simulation on subgrade.After 3 hours of simulated rainfall,the experimental results are obtained.For example,in group A,the bearing capacity of condition 1 ’and condition 2’ is reduced by27.8% and 15% respectively,and the settlement is 24.7mm and 20.1mm;The bearing capacity of group B and group C decreased by 16.6%,and the settlement was 22.1mm and23.1mm.The simulated rainfall test shows that the bearing capacity of the soil mixed with curing agent decreases after rainfall,but it can still meet the requirements of the experiment;The bearing capacity of original soil or natural soil decreases directly after rainfall.The main factor is the poor hydration resistance and strong hydrophilicity of soil particles.Once they touch water,they directly affect their mechanical properties,resulting in the reduction of its bearing capacity and poor stability. |
